Method of manufacturing artificial tooth-fronts.



. STEELE.

METHOD OF MANUFACTURING ARTIFICIAL TOOTH FRONTS.

N FILED MAY 15,191 LUSQfifi.

Patented Dec. 23, 1913.

FIN

THOMAS STEELE, OF COLUMBUS, OHIO, ASSIGNOR TO THE COLUMBUS DENTAL M'ANU-FACTUBIING: COMPANY, OF COLUMBUS, OHIO, COEPOBATIFON OF OHIQ').

METHOD OF MANUFACTURING ALG'IKYEICIAL TOOTH-FRGNTS.

Specification of Letters Patent.

Patented lik cc. 23, M913.

Application filed May 15, 1911. Serial 1 !0. 627,287.

To all whom it may concern Be it known that l', Tnonns STEELE, a citizenof the United States, residing at Columbus, in the county of Franklinand State of Ohio, have invented certain new and useful Improvements inMethods of Manufacturing Artificial 'lootlrFronts, of whichthe'following is a specification.

My invention pertains to an improved method of manufacturing artificialtooth fronts and is particularly directed. toward providing an improvedseries of correlated steps for manufacturing tooth fronts of a standardform and size and in such a manner that absolute accuracy of measurementand construction is attained with a minimum difiiculty. It is intended,by this method, to form the various surfaces of the tooth front and inthe act of forming these various surfaces to effect a coactive measuringaction between the parts in such a manner that a perfect tooth front isformed. By way of illustration of some of the different series of stepswhich may be taken to attain the desired result, and at the same time bewithin the spirit of the method utilized by me, attention is called tothe accompanying drawings.

Referring to the drawings specifically and with particular reference tomy preferred method: Figure 1 is a transverse section of a tooth frontin its condition of removal from the mold and in rough form and showingthe hole and/ slot baked therein, but considerably off center, Fig. 2 isa transverse section of the baked tooth with its rear surface smoothedto a practically perfect plane. Fig. 3 is a transverse section of thetooth front after the slot has been accurately centered, which ispreferably effected by means of a perfect plane surface in conjunctionwith a gripping means for the tooth front and a relatively travelingcutter, which cutter must necessarily travel in a line of predeterminedlength and relation to the plane surface and to the means for holdingthe tooth, Fig. a is a transverse section of the tooth after the holehas been centered, which is desirably effected by the provision of acentering element to be straddled by the walls of the slot in the toothfront. It will of course be understood that this centering element bearsa determinate relation to a boring tool or tools for correcting theinaccuracy of the bore. This sets forth the relation of the successivesteps of my preferred method of coactively centering the surface of thetooth front. Another method is illustrated by other figures of thedrawing, as follows: Fig. 5 is a cross section of an artificial toothfront as removed from a mold in rough form and with both the hole andslot oil center, Fig. (5 is a cross section showing the tooth frontwith'its rear surface ground to a n'aetically perfect plane, Fig. 7 is across sectional view of the tooth front showing its rear surface groundto a perfect plane as in the preceding figure and showing the bore inthe tooth accurately centered, in the effecting of which the planesurface plays an important part as does a holding mechanism formaintaining the tooth front in a definite position on its rear surfaceand in proper relation to a boring device, Fig. 8 is a cross sectionalview of the tooth front in its com. plcted condition and with its rearsurface ground to a perfect plane its bore accurately centered as beforestated-and its slot properly centered which is effected through themedium of a centering element upon which the tooth front is mountedthrough the utilization of the properly centered bore. These last fourfigures are designed to show a second way of effecting the desiredresult in accoroanco with my method. Fig. 9 is a rear elevation of thetooth front, and, Fig. 10 is an edge view of one of the tooth fronts.

The science of manufacturing artificial teeth and tooth fronts, is onethat is subject to and effected by a number of elements andcircuu'istanccs solely its own. Chief among these circumstances, is theliability of shrinkage. It is a known fact in the art of manufacturingtooth fronts, that the degree of shrinkage in a. tooth during baking isin the neighborhood of 26%. Necessarily, this shrinkage accompanied by acertain amount of distortion. The degree of shrinka 'e and distortion isordinarily regulated and controlled by the length of baking and ofcourse necessarily affected by the uneven packing of the mold.Furthermore, which is of equal importance, it is customary in makingthese tooth fronts to utilize two or more different grades ofmaterial,

which in fusing show relatively different degrees of shrinkage. Thiswill be readily understood when it is pointed out that the masticatingsurface of the tooth fronts is necessarily of a rigidity of a porcelainnature, whereas it is advisable to provide the walls of the slot andhole of a less brittle quality of material. The making of the teeth indifferent colors, also efi'ects this in a measure and when a pluralityof difierent materials is used, it will bewell understood thatthe'shrinkage and distortion will be necessarily uncertain andungovernable.

The present invention and method of re pairing tooth fronts is thoughtto obviate any draw-back attendant upon the featuresnoted above.

What I claim, is

l. The method of treating an artificial tooth front, after it has beenbaked with a longitudinal bore and a communicating transverse slottherein, commensurate with the length of said bore, to form the varioussurfaces of the tooth front and in the act of forming these varioussurfaces to effect a coactive measuring action between the parts in suchmanner that a perfect tooth front is formed, which consists in smoothingthe rear surface of the tooth front to a perfect plane, then accuratelycentering the transverse slot with the said plane as a guide, andfinally accurately centering the bore with the transverse slot as aguide.

2. The process of making artificial tooth fronts which consists inmolding the' biscuit with an elongated slot in its rear face and acommunicating bore disposed longitudinally of the tooth front, bakingthe biscuit, smoothing the rear face of the tooth front eater osaeea toa perfect plane, centering the bore accurately both longitudinally andtransversely with reference to the plane of the back of the tooth frontand finally accurately centering the said slot with reference to thebore and the plane of the back of the tooth front,

whereby exact interchangeable duplicates of tooth'fronts are made.

3. The method of treatmg artificial tooth fronts, after they have beenbaked with a transverse slot and a longitudinal bore communicating withsaid slot and of greater length than said slot, to form the variousbearing surfaces of the tooth fronts and in the actof forming saidsurfaces to effect a co-active measuring action between the saidsurfaces in such manner that an accurately interclmngeable tooth frontis formed, which consists in first grinding the rear surface of thetooth front to a perfect plane, then accurately centering the transverseslot with said plane as a guide, then accurately centering the bore withthe transverse slot with respect to the slot using the slot as a guide,grinding the bore throughout its length parallel to the plane of back ofthe tooth front and of length than the said slot.

In testimony whereof I affix my signature in presence of two witnesses.

THOMAS S EELE.

-Witnesses lV. L. TRUESDELL, EDWIN P. CORBETT.

